This invention relates generally to wellbore casings, and in particular to wellbore casings that are formed using expandable tubing.
Conventionally, when a wellbore is created, a number of casings are installed in the borehole to prevent collapse of the borehole wall and to prevent undesired outflow of drilling fluid into the formation or inflow of fluid from the formation into the borehole. The borehole is drilled in intervals whereby a casing which is to be installed in a lower borehole interval is lowered through a previously installed casing of an upper borehole interval. As a consequence of this procedure the casing of the lower interval is of smaller diameter than the casing of the upper interval. Thus, the casings are in a nested arrangement with casing diameters decreasing in downward direction. Cement annuli are provided between the outer surfaces of the casings and the borehole wall to seal the casings from the borehole wall. As a consequence of this nested arrangement a relatively large borehole diameter is required at the upper part of the wellbore. Such a large borehole diameter involves increased costs due to heavy casing handling equipment, large drill bits and increased volumes of drilling fluid and drill cuttings. Moreover, increased drilling rig time is involved due to required cement pumping, cement hardening, required equipment changes due to large variations in hole diameters drilled in the course of the well, and the large volume of cuttings drilled and removed.
The present invention is directed to overcoming one or more of the limitations of the existing procedures for forming wellbores.
According to one aspect of the present invention, a method of driving a pipe into a subterranean formation is provided that includes driving a hole into the subterranean formation using an expansion cone.
According to another aspect of the present invention, a method of forming a casing in a wellbore is provided that includes driving a hole into the bottom of the wellbore using an expansion cone and radially expanding the casing using the expansion cone.
According to another aspect of the present invention, a method of forming a support structure in a shaft is provided that includes driving a hole into the bottom of the shaft using an expansion cone and radially expanding the support structure using the expansion cone.
According to another aspect of the present invention, a wellbore casing is provided that includes an expanded tubular member positioned in intimate contact with the walls of a wellbore. The expanded tubular member is positioned by the process of: driving a hole into the bottom of the wellbore using an expansion cone and radially expanding the tubular member using the expansion cone.
According to another aspect of the present invention, a support structure is provided that includes an expanded tubular member positioned in intimate contact with the walls of a shaft. The expanded tubular member is positioned by the process of: driving a hole into the bottom of the shaft using an expansion cone and radially expanding the tubular member using the expansion cone.
According to another aspect of the present invention, an apparatus for driving an opening into the bottom of a shaft is provided that includes an expansion cone adapted to radially expand a tubular member and a hammer for driving the expansion cone into the bottom of the shaft.